1. Field of the Invention
This invention relates to an analyzer for quantitatively analyzing the activity or concentration of a specific ion contained in an aqueous liquid sample, for example, a wine, other beverage, service water, or, particularly, a body fluid (blood, urine, saliva or the like), by potentiometry by use of a slide type ionic activity measuring device.
2. Description of the Prior Art
As disclosed in, for example, Japanese Patent Publication No. 58(1983)-4981, and Japanese Unexamined Patent Publication Nos. 58(1983)-156848 and 58(1983)-211648, there has been proposed a slide type ionic activity measuring device for receiving a liquid sample fed in drops and measuring the activity of a specific ion contained in the sample.
The slide type ionic activity measuring device comprises at least one ion selective electrode pair consisting of ion selective electrodes generating potential corresponding to the ionic activity of a predetermined ion, and a porous bridge disposed for communication between the electrodes of the ion selective electrode pair. A reference solution containing a predetermined ion whose ionic activity is known is fed in drops to one of the electrodes of the ion selective electrode pair, and a sample solution wherein the activity of the predetermined ion is unknown is fed in drops to the other of the ion selective electrode pair. By the effect of porous bridge, the reference solution and the sample solution contact each other to achieve liquid-junction, i.e. electrical conduction therebetween. As a result, a difference in potential proportional to the difference in the activity of the ion between the reference solution and the sample solution arises between the electrodes of the ion selective electrode pair. When the difference in potential has been measured, it is possible to determine the activity of the predetermined ion in the sample solution on the basis of a calibration curve determined in advance (by use of Nernst's equation).
In order to measure the ionic activity by use of the aforesaid slide type ionic activity measuring device, an analyzer provided with functions of feeding of a reference solution and a sample solution and measurement of a difference in potential should preferably be used. Such an analyzer is described in, for example, U.S. Pat. No. 4,257,862 and Japanese Patent Application No. 59(1984)-12794. The conventional analyzer of this type is arranged so as to manually transporting the slide type ionic activity measuring device to a potential measuring section after feeding of the reference solutoon and the sample solution, and to make potential measuring probes contact the electrodes at the potential measuring section. However, with this configuration, the fed solutions and the condition of liquid-junction therebetween are disturbed by vibrations caused during transporting of the slide type ionic activity measuring device, and as a result a measurement error arises. Though this problem can be prevented to some extent by carrying out the operation of transporting the slide type ionic activity measuring device carefully, the operating efficiency becomes low in this case.